Labour is confident of securing at least a 60-seat Commons majority in 2015, according to the party's general election chief.

Tom Watson said such a convincing win was "realistic" after the shadow cabinet approved his strategy to concentrate on 106 key marginal constituencies.

Under the ballot box blueprint, the opposition expects each of its 255 sitting MPs to hold their seats with little problem.

It is to concentrate funds on training US-style community organisers and using social media in target areas in a bid to emulate Barack Obama's electoral success in the US.

Among ambitious aims is ejecting Liberal Democrat deputy leader Simon Hughes from the seat he has held for 30 years, which would require a 9.6% swing.

Tom Watson has drawn up a target list

The vast bulk of the list is made up of the constituencies - four-fifths held by the Tories - which would be won on a uniform national swing.

Only 30 candidates have so far been selected in the target seats but the process is expected to be completed by the summer.

The party is aiming to train up to 1,000 party members to be professional organisers, using US expert Arnie Graf, who trained a young Mr Obama.

It is also using the American "Nation Builder" IT system to make the best use of social media - now regarded as a key campaign tool.

Mr Watson contrasted the Labour "offensive" strategy of targeting only other parties' seats with a Tory plan to defend 40 of its own and win another 40.

If successful, it would result in a Labour majority of 80 - well above the 66-seat advantage secured by Tony Blair in Labour's last general election win in 2005.

Asked if he was confident of winning, Mr Watson said: "Yes, 100%. I would not be presenting this if I did not think it was realistic."

Mr Watson said the party had "done a lot of research" based on recent election results and demographic changes to come up with the list.

Of the 106, 86 were won in 2010 by Conservatives, 16 by Lib Dems, two by Plaid Cymru and one each by the Scottish National Party and the Green Party.

Other than Mr Hughes' Bermondsey and Old Southwark seat and two other Lib Dem-held constituencies - Bristol West and Leeds North West - they are all marginals that would all be won by Labour on a swing of 7.4% or lower.

One omission from the list is Bradford West, where Respect's George Galloway scored a shock by-election victory over Labour last April.

Mr Watson said it was not included because it was expected to be won back relatively easily despite Mr Galloway's 10,000-vote majority.

He joked that it had been "very tempting" to include Deputy Prime Minister Nick Clegg's Sheffield Hallam seat.

Sitting MPs who enjoyed only wafer-thin majorities were aware of the intent not to target resources at them, Mr Watson said.

And the party was lucky that many of those were "very good campaign-focused MPs" such as Toby Perkins, Gloria De Piero and Ian Austin, he added.

The latest YouGov opinion poll, published at the weekend, had Labour on 43%, the Tories on 32%, Lib Dems on 10% and Ukip on 9%.